Revert "usb: msm_otg: Migrate to clock apis for XO voting"

This reverts commit 7dd2266a.

It was a mistake to move the usb driver to the clock apis for XO
buffer voting. Due to an RPM design CXO and D0 are the same but
we would like to hide that from the users of the buffers.
Therefore the msm_xo driver itself remaps the D0 buffer request
to the cxo clock until the RPM is fixed.

Change-Id: I230de55d30a49fa5bcf0d07f40453f1e09c4a9b1
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>